1. Field of the Invention
The present invention pertains to dynamometers or dynamic testing apparatus for measuring the performance of a vehicle. In particular, the present invention concerns a dynamometer particularly suitable for measuring the power characteristics of a motorcycle.
2. Description of the Prior Art
Ever since the development of the engine and the motor, man has sought means to accurately measure the power characteristics thereof. Since the horsepower delivered by a rotating shaft is defined as 2.pi.nT/33,000, where n equals rpm and T equals torque in footpounds, output horsepower can be determined by measuring the speed and the torque of the output shaft. The speed can be measured directly by means of a tachometer. Mechanical power measuring devices called dynamometers have been developed to measure the torque.
There are basically two types of dynamometers: (1) those absorbing the power and dissipating it as heat and (2) those transmitting the measured power. In the transmission dynamometer, the torque is measured by means of strain guage elements bonded to the transmission shaft. There are several kinds of absorption dynamometers, one of which is the Prony Brake which applies a friction load to the output shaft by means of wood blocks, flexible bands or other friction surfaces. The fan brake and water brake are other types of dynamometers which are known.
Many types of dynamometers have been specially developed for measuring the power characteristics of automobiles. Some recent examples of automobile dynamometers may be seen in U.S. Pat. Nos. 3,277,702; 3,491,587; and 3,651,690. Although some of the principles involved may be similar, dynamometers developed for automobiles are not necessarily desirable for use on motorcycles.
In the past, there has been little concern, other than by manufacturing companies, for measuring the power characteristics of motorcycles. However, with the greatly increased interest in and use of motorcycles, there is an increasing demand for devices which accurately measure the performance of these motorcycles. An example of a motorcycle dynamometer may be seen in recently issued U.S. Pat. No. 3,733,894. Other motorcycle dynamometers are commercially available.
Since cyclists are quite mobile and may be found in many different locations, it is desirable that motorcycle dynamometers be as portable as possible. It is also desirable that such dynamometers be self-sufficient, relying as little as possible on outside power sources and auxiliary apparatus such as plumbing for cooling water, etc.
Most of the commercially available motorcycle dynamometers leave a great deal to be desired in accuracy. The apparatus for measuring either one or both of the torque and speed of a motorcycle may not be totally reliable. Furthermore, most of the motorcycle dynamometers available do not provide the road wind normally encountered by a motorcycle under normal operating conditions. Those that do, do so inadequately or by means of a relatively small fan or blower which requires auxiliary power sources.
In addition, most motorcycle dynamometers of the prior art utilize some form of load or torque arm for measurement of torque. Such devices are relatively expensive and sometimes difficult to calibrate. Furthermore, some of the motorcycle dynamometers of the prior art are hazardous to the operator, cycle and bystanders.